1. Field of the Invention
The present invention relates to a liquid discharge recording head and a recording apparatus, and more particularly to a liquid discharge recording head capable of stably discharging droplets.
2. Description of the Related Art
When a recording operation is performed using a liquid discharge recording head (hereinafter, occasionally referred to as recording head), very small droplets (mist) may be discharged in addition to mainly used droplets (hereinafter, referred to as main droplets). Hereinafter, such very small droplets are referred to as small droplets.
The small droplets adhere to a surface with droplets-discharging ports (face) by airflow generated when a liquid is discharged from the recording head and when the recording head performs reciprocation scanning. When the small droplets adhere to the face and are accumulated on the face, discharging of the main droplets may become unstable, possibly deteriorating image quality of a recorded image. Owing to this, cleaning of the face with a blade that wipes out the face, and a recovery operation by sucking the droplets from the recording head have to be frequently performed during the recording operation. The recovery operation may reduce the speed of the recording operation.
Japanese Patent Laid-Open No. 11-5307 discloses a recording head to prevent unstable discharging. The recording head disclosed in Japanese Patent Laid-Open No. 11-5307 includes a flow passage forming member having a plurality of discharging ports. An evaporation suppressing groove is formed near the discharging ports.
The evaporation suppressing groove is hydrophilic, and hence, can hold small droplets adhering to the face. Accordingly, the humidity around the discharging ports is increased, and hence evaporation of the droplets from the discharging ports is prevented, thereby improving stability of discharging.
Meanwhile, in order to increase the speed of the recording operation, it is effective to increase a drive frequency of discharging the droplets. However, when the drive frequency is increased, the small droplets adhering to the face of the flow passage forming member may be easily moved by, for example, an inertial force applied when the recording head performs reciprocation scanning.
By the movement of the small droplets, the small droplets are combined and become large droplets with larger diameters. When the face may be excessively wet, the droplets may enter the discharge ports, resulting in unstable discharging or non-discharging of the droplets. In particular, this phenomenon may be noticeable when the recording head is a long recording head having more nozzles.
To address such a problem, Japanese Patent Laid-Open No. 2006-103320 discloses a recording head having another hydrophilic groove formed in the face.
The recording head disclosed in Japanese Patent Laid-Open No. 2006-103320 includes a flow passage forming member having a plurality of arrayed nozzles. Discharging ports of the nozzles are open to the face. The face has formed therein a circular hydrophilic groove surrounding all discharging ports. In addition, another hydrophilic groove is formed on both sides of the above hydrophilic groove in a main-scanning direction (a direction in which the recording head reciprocates during the recording operation), so as to extend in a sub-scanning direction (a direction perpendicular to the main-scanning direction).
Accordingly, the small droplets adhering to the face are dispersed to the plurality of hydrophilic grooves. Thus, the small droplets are prevented from locally staying in the hydrophilic grooves, and from leaking from the grooves.
However, with the recording head disclosed in Japanese Patent Laid-Open No. 11-5307 or 2006-103320, when the recording head is driven with a high frequency or when the droplets are continuously discharged, the small droplets may locally adhere to the face, and the amount of droplets may exceed the capacity of the hydrophilic grooves.
The small droplets exceeding the capacity may leak from the hydrophilic grooves by the inertial force applied when the recording head performs reciprocation scanning. Thus, to keep the image quality high during high-speed printing, the droplets in the grooves have to be drained after a predetermined recording operation.
The drain of the droplets is performed by sucking the droplets from the inside of the hydrophilic grooves while the face of the recording head is covered with a recovery unit.
The recovery unit includes a cap, a droplet-absorbing member provided in the cap, and a suction unit. A peripheral edge of the cap contacts an upper surface of a chip plate surrounding the flow passage forming member, so that the face is airtight. An air suction pipe is connected to the cap. The air suction pipe sucks the air in the airtight space.
In this state, by sucking the droplets by the sucking unit, the droplets staying in the hydrophilic grooves are drained.
In the recording head disclosed in Japanese Patent Laid-Open No. 11-5307 or 2006-103320, the pressure of the entire face covered with the cap is reduced when suction is performed during a recovery process.
With this configuration, it is difficult to collect all small droplets in the hydrophilic grooves, and the small droplets still remain in the hydrophilic grooves.
If the small droplets remain in the grooves, holding effect of the grooves for newly generated small droplets may be deteriorated. Hence, a liquid may leak from the grooves, the face may be wet, and discharging may become unstable.
To avoid this, the recovery process has to be frequently performed. This, however, decreases the speed of the recording operation.